In the field of conveying aggregate material, such as coal or other minerals and rock, it is necessary to keep the upper or working surface of the conveyor belt free of debris, such as a build-up of coal dust from the coal being conveyed. Not only is this important in a mining environment, but is also necessary for handling of the coal in a power plant or the like. The problem of debris build-up becomes particularly acute in a situation where there is moisture in the atmosphere. If the debris is not removed, the conveying efficiency is reduced due to the extra weight. This provides a substantial extra burden to the driving motor for the belt pulleys. In some instances, the build-up can disrupt the tracking of the belt and even cause the belt to come off of the pulleys and guide rollers. In this instance, the downtime of the conveyor can cause substantial losses in the mine and/or the power plant.
During recent years, the technology of scraper blades has progressed relatively slowly. A typical blade in use today is molded of urethane rubber and has a generally curved, concave face directed toward and parallel to the surface of the conveyor belt on a pulley. This blade shape has not changed over the past several decades.
One example of a scraper blade having a concave face on the pulley side of a conveyor is the Swinderman U.S. Pat. No. 4,917,231. The emphasis of this blade is to provide a constant angle of attack against the conveyor belt as the distal edge wears. There is no provision for blocking the build-up of debris between the downstream face of the blade on the pulley side and the operative face of the belt. Indeed, experience has shown that debris, especially in wet conditions, does tend to form in this space between the blade and the belt and eventually leads to a build-up sufficient to cause planing of the blade. When this occurs, the distal edge for scraping is forced away from the surface of the belt by the hard packed debris, thus destroying the scraping efficiency.
Other efforts attempting to improve the technology of the scraper blade for a conveyor belt is typified by the Gordon U.S. Pat. No. 5,222,589. In this patent, and in others like it, changes have been made in the transverse holder that provides a mount for the base of the blade. Little change in the efficiency of operation of the blade, particularly in the area of preventing debris build-up, is realized by use of this arrangement. Again, the shape of the blade is provided with a concave face on the pulley side. As is usual, the axis of generation of the concave face is parallel to the belt and the plane extending through the blade and the distal edge for scraping. With this arrangement, as in the arrangement of the '231 patent, there is no localized vortex action that can be generated to block the build-up.
Another area of development of the scraper blade art is characterized by making the blade S-shaped with the base being mounted in a pocket in the transverse holder; see Puchalla, U.S. Pat. No. 5,573,102. While this patent appears to recognize the problem of build-up of dirt or debris, the only modification of the scraper blade to attempt to correct it is to provide protection aprons, both on the pulley side and the back side of the blade. The aprons add substantial expense to the blades and, insofar as is known, do not solve the problem of dirt/debris build-up.
Thus, considering the problem identified and the failure of the prior art to address and solve the problem, what is needed is a new approach to the scraper blade that can be relied upon for high efficiency to block debris build up, as well as being low in cost and easy to manufacture. The blade should be interchangeable with blades that are already on the market. The blade should be constructed so as to provide in all instances localized multi-plane vortex action to prevent build-up sufficient to cause planing of the blade.